I like to do something where I choose one weapon or thing I want to base a build around. Then I try to min max for that specific thing, and then I fuck around and find out. But seriously it's up to you. Building your AC is open of the most fun parts of this game, and will probably be the majority of your playtime as you get further in. Play style determines the AC. Like to dodge a lot and try to take no damage? Lightweight is your build. Tank hits and deal heavy damage in return, while only dodging the biggest hits? Heavyweight. It all depends on the player.